Humidifiers are used to condition the air. For example, a humidifier may be used in a residential or commercial environment to increase the moisture in the air for comfort or other purposes. When an indoor environment is heated, it often needs to be humidified to provide an improved comfort level. Humidifiers may be portable such that they can be easily moved or used in a location without a built-in humidifier. Portable humidifiers have water reservoirs and water flow passages, which may become contaminated with microorganisms living in the water. The contaminated water in the humidifier has the potential to produce contaminated humidified air or contaminated aerosolized water.